Peni was interested when she had been chosen by some lucky contest winners. However she was a little bored by the idea of just giving them what they wanted. So she made a game out of it. Both winners were subject to a special device of hers. Linking each of their Libido to their size.
The rules were simple, the more you cum the more you shrink, she'd only return them to normal size if they could last the night. Being allowed to engage in any desire they wished of hers.